Concentrations of unconjugated and glucuronated C-21, C-19 and C-18 steroids have been measured in follicular fluid obtained from women hyperstimulated by a combination of clomiphene citrate, pergonal and hCG. Pregnenolone and its glucuronide are found at approximately 5% of the progesterone values (14,395 +/- 2300 ng/ml). Concentrations of dehydroepiandrosterone glucuronide, androst-5-ene-3 beta, 17 beta-diol glucuronide, dihydrotestosterone glucuronide, androstane-3 alpha, 17 beta-diol glucuronide and androstane-3 beta, 17 beta-diol glucuronide are 2-6-fold higher than those of the related unconjugated steroids, while testosterone glucuronide levels are lower than those of testosterone. The concentrations of androsterone glucuronide reach almost 30-fold those of androsterone (2.56 +/- 0.35 ng/ml). By contrast, estradiol and estrone concentrations are 10-20-fold higher than those of conjugated steroids. Measurement of plasma steroid glucuronides indicated that the concentrations in circulation are markedly lower than those detected in follicular fluid. Our data suggest that the ovary in humans may be a site of glucuronidation.